Manufacture of cellulose organic acid ester crepe yarns



.Aug. 15, 1939. J..G. MCNALLY MANUFACTURE OF CELLULOSE ORGANIC ACIDESTER GREYS YARNS Filed Jan. 21, 1957 James GM NaIly I INVENTOR.

BY gwnwa ATTO EY5 Patented Aug. 15, 1939 MANUFACTURE OF CELLULOSEORGANIC ACID ESTER CREPE YARNS James G. McNally, Rochester, N. Y.,assignor to Eastman Kodak Company, Rochester, N. Y., a corporation ofNew Jersey Application January 21, 1937, Serial No. 121,555

8 Claims. (Cl. 57-140) these warps.

This invention relates to crepe yarns and crepe fabrics and theirproduction, and more particularly to crepe yarns and fabrics made oforganic acid esters of cellulose, such as cellulose acetate, cellulosepropionate, cellulose butyrate, cellulose acetate-propionate, celluloseacetate-butyrate and the like.

This application is in part a continuation of my copending applicationSerial No. 62,007, filed February 1, 1936.

It is customary in the art to employ for the manufacture of crepefabrics, highly twisted yarns, comprising cotton, natural silk, wool, orthe regenerated cellulose type of synthetic yarn, usually referred to asrayon and referred to herein as rayon, the highly twisted yarn beingreferred to as crepe yarn. Cloth constructions are very well knownwherein crepe yarns are used either in warp or filling or both, but thecrepe filling typeis the more popular, which condition is largely due tothe lower cost of production of the crepe filling fabric, The presentdiscussion is.

therefore, more particularly directed to fabrics employingv crepefilling yarns, although it is understood that the remarks herein mayrelate to warp crepes as well, with modifications such as are obvious toa textile technician.

For certain novelty effects crepe yarns are used which comprise amixture of materials such as cotton-natural silk, natural silk-rayon,natural silk-cellulose acetate yarn, or rayon-cellulose acetate yarn.These mixtures are employed either as separate threads or two threadsmay be twisted together before weaving for the purpose usually ofdecreasing the cost of production of the fabric or of producingcross-dye or other novelty effects. It may be pointed out, however, thatin crepe constructions where cellulose acetate yarn is used in thefilling it is used in conjunction with a crepe filling yarn of someother material and has no active part in producing the crepe effect.

Cellulose acetate yarns have found extensive use as warp yarns for crepefabrics because of the highly desirable properties of fabrics made withThe filling yarns usually used in these popular constructions is rayonor natural silk crepe yarn and the presence of two types of yarn, i. e.,cellulose acetate and rayon or silk, leads to dyeing dimculties infinishing the goods owing to the fact that cellulose acetate yarn is, ingeneral, unaffected by dyes for rayon or natural silk and, similarly,dyes suitable for coloring cellulose acetate yarn are not suitable forthe other materials. It. therefore, becomes neces sary to use separatedyes for coloring the constituent yarns of these fabrics, which is aninconvenience and added expense. Aside from the desirability ofeliminating this dyeing difliculty with acetate warp crepes, it has beenfound that crepe fabrics made entirely of cellulose acetate yarns (bothwarp and filling) show to an enhanced degree the desirable properties ofdurability, non-creasabillty, and excellent hand and draping propertieswhich are obtained by using cellulose acetate yarns in the warp alone.

In order that the novel features of the instant invention may be clearlyapparent, a brief description of the way crepe fabrics are at presentmade, using rayon or natural silk crepe filling, is here given, theessential features of such present processes being the following:

(1) Low turn rayon or natural silk yarn is soaked in a solution of sizethe excess solution removed and the yarn dried.

(2) The sized yarn is twisted, usually on an up draft twister, to form30 to turns per inch, depending upon the denier of the yarn and the useto which it is to be put,

(3) After ,the operation (2) the yarn has a tendency to untwist. Toovercome this difficulty, the yarn is steamed while wound a on spools toset; the twist of the yarn.

(4) The filling yarn is wound on cops and used in the customary looms increpe fabric constructions.

(5) The greige goods from the loom are subjected to a boil off treatmentin hot soap solution to remove the size from the yarn; the fabricshrinks widthwise preferentially and develops a pebbled appearancecharacteristic bf crepe fabrics.

(6) The fabric is dyed on a winch machine, dried on a slack dryer andframed out to the desired width on a tentering frafne.

The finished crepe fabric has two outstanding characteristics:

(1) A pebble or rough surface which varies in appearance depending onthe type of crepe produced.

(2) Extensibility and elasticity which differentiate the cloth fromtightly woven -constructions such as taffetas or satins.

A popular construction for producing a rayon filled Canton crepe is asfollows:

Warp-112 ends per inch, denier dull cellulose yarn, 40 filaments, 4turns per inch.

Filling.'52 picks per inch of denier rayon twisted to 50 turns per inch,the filling construction being two picks of right yarn alternating withtwo picks of left twist yam. The greige goods are woven 50 inches widein the. loom,

When this fabric is woven, as indicated, into greige goods and boiledof! it shrinks wldthwise from 50 inches to 28-30 inches and develops abumpy, finely pebbled surface. On framing in the tentering machine, thecloth is brought back to 39-40 inches in width and this represents ,the

finished dimension, The cloth shrinks longitudinally about 10-15 percent.

I am aware that the prior art reports many attempts to produce acellulose acetate crepe yarn, It was first proposed in the art toproduce cellulose acetate crepes by substantially imitating the methodof producing crepe from natural silk, involving sizing, twisting,setting weaving and boiling off. Since that time it has been. variouslyproposed to subject the yarn to shrinking treatments before weaving, totreat fabrics woven from cellulose acetate crepe yarns with bathscapable of swelling cellulose acetate, to partially saponify thecellulose acetate yarn before twisting, to incorporate water-solublematerials in the cellulose acetate crepe yarn, or to combine celluloseacetate yarns having different degrees of twist, using a relatively lowtwist in the doubling operation. It has further been proposed to producecloths of cellulose acetate having a puckered or crepe-like appearanceby subjecting cloths woven at least partly of cellulose acetate yarn totreatments calculated to cause differential shrinking of the variousyarns contained in the fabric. It may be said, however, that theseprocesses result in such very slight effects as to be scarcelyperceptible (widthwise contraction or shrinkage, due to creping,produced in the boil-off, not exceeding 10 15%) and are of no commercialimportance, as the resulting fabrics have none of the propertiesexhibited by the rayon-filled Canton crepe.

In addition to the above-mentioned methods of producing celluloseacetate crepe yarns and fabrics, numerous other expedients have beensuggested. For example, it has been proposed to produce acetate crepeyarn by treating the yarn with hot (95-100" C.) water during theinsertion of at least the last part of the crepe twist, it apparentlybeing the theory of the proponent of this procedure that the crepingability of the yarn results .from the simultaneous application ofstretching and twisting forces to the material while in a softenedcondition and that the yarn must be stretched at such temperatures asrender it plastic and ductile. The type of crepe yarn resulting fromsuch a process is characterized by the fact that it is stretched from 5%to 30% of its original length, has a denier of 95-115% of that of theoriginal yarn before twisting, and has a specific gravity of- 85-90% ofthe actual specific gravity of the original filaments. It is alsocharacterized by the fact that the surface of the threads are smooth andcylindrical as opposed to the rough feel of a viscose crepe yarn or of acellulose acetate yarn which has been crepe twisted by the methodhereinafter described.

I am further aware that it has also been proposed to use variousmodifications of the process referred to in the preceding paragraph,using dry steam, wet steam, organic liquids, etc., as the yarn treatingmedium. When using either one of the methods last referred to, whensufficient tension is employed to induce the necessary degree of stretchin the yarn, the product is characterized by a smooth appearance and is,as stated, free from kinks.

I have now discovered that a commercially successful cellulose acetatecrepe yarn can be made by a departure from the prior art wherein,following my invention, the crepe twist is inserted in the yarn while itis swollen with water but under such mechanical conditions that the yarnexperiences a minimum of longitudinal extension during the twistingprocess. The temperature of the water used to soften the yarn prior toor during the twisting operation is of importance only inasmuch as thisfactor is one of several that determine the longitudinal extension givento the yarn. The other factors are the chemical composition anddynamometric properties of the yarn used, the length of time of soakingand the longitudinal tension on the yarn during the twisting process.When using cellulose acetate yarn of the type commercially availableunder the name Eastman acetate yarn and when twisting on the type ofring twister hereinafter described, I find that 'the longitudinaltension should not exceed 0.15 gram per denier when twisting the yarnwet with water at approximately 60 C. as at higher tensions at thistemperature the yarn is given excessivelongitudinal extension resultingin an inferior quality of crepe yarn. If the mechanical conditions oftwisting can be so arranged to provide for sufficiently low tensions toprevent longitudinal extension, somewhat higher temperatures may beemployed for example as high as 85 C. with a tension of approximately0.1 gram per denier. Correspondingly, at lower temperatures, somewhathigher tensions are permissible, for example at 20 C. I may employtensions amounting to 0.20 gram per denier.

Opposed to the teachings of the prior art, I have found that in theproduction of true crepe fabrics from cellulose organic acid ester yarnsthe yarn need not be sized before, during, or after twisting, but needmerely be softened before twisting, preferably without sizing; thetwisted yarn should not be given any treatment which thermoplasticallymolds the yarn, such as hot water treatment, or treatment with hot steamor other hot liquids or vapors; and the woven fabric should besufficiently softened in the boiloff bath to permit the crepe action inthe twisted yarn to assert itself. Furthermore, opposed to the resultsobtained by the prior art in attempting to produce cellulose acetatecrepes I have found that it is possible to produce a cellulose acetatecrepe by my invention which has a widthwise contraction or shrinkage ofapproximately 404.30%, a condition which is necessary in the productionof true crepe effects in the fabric.

One feature of the product of my invention wherein it differs fromcellulose acetate crepe yarns made by stretching the yarn prior to,after or simultaneously with the twisting process is that my crepe yarnhas good breaking strength and good extensibility at break whereas thesedesirable features are lacking in the stretched yarns. In order to weavesuccessfully on the type of power looms universally used for weavingcrepe fabrics, an acetate crepe yarn must be able to stretchconsiderably without breaking and although the requisite extensibilityof the yarn will vary somewhat depending on exact weaving conditions, Ihave found that a cellulose acetate crepe yarn having an extensibilityof under 15% breaks so frequently in the loom as to render its useuneconomical. Yarn made by the process herein described and claimed hasan extensibility before breaking ranging from 15-26% and operates withhigh efllciency in modern rayon or silk type automatic looms. I havefound that the stretch-twisting process of twisting' gives acetate crepeyarns having extensibilities well below this lower limit of 15%. Theyare usually in the range of 8-10% and I have further determined thatsuch yarns cannot be employed in the operation of an automatic loom withany degree of efficiency such as would render their use economi callypossible even if they could produce a desirable crepe fabric.

This invention has as its principal object to produce from celluloseorganic acid ester yarns a crepe yarn which is useful as filling or warpor both in the production of fabrics produced exclusively or partiallyfrom such yarns. A further object is to produce a crepe yarn without thenecessity of employing a sizing bath, without using liquids or vaporsheated to a high temperature or any other agency which thermoplasticallymolds the yarn. Another object is to produce a true crepe fabriccomposed either exclusively or partially of cellulose organic acid esteryarns. Other objects will appear hereinafter.

These objects are accomplished by the following invention which, in itsbroader aspects, comprises the treatment of the yarn with a hot aqueousliquid such as water or a weak aqueous solution of soap, or similaragent which has a moderate softening action on the cellulose organicacid ester material of the yarn, at temperatures ranging up to about C.,then giving the yarn a high degree of twist while in a softenedcondition and under such tensions as at the temperatures employed willresult in a permanent elongation of the filaments of less than 5%.

As indicated, for the purpose of softening the yarn, I have successfullyemployed water alone, but I may employ mixtures of water and othersoftening agents, aqueous emulsions of vegetable, animal or mineraloils, solutions of soaps or other wetting or dispersing agents andsolutions of colloidal film-forming materials, which solutions have asoftening action such as gelatin, starch, water-soluble polyvinylresins. of this size in no way accounts for the creping power of thecrepe yarn produced by following this invention as I obtained as goodcreping results when using a softening bath which contains no filmforming or colloidal material. The function of the size, when used, isto form a protective coating on the yarn which binds the filamentstogether thereby protecting them from mechanical ahrasion during weavingand the presence of the size on the crepe yarn is of no consequence inthe production of the crepe effect by a suitable aqueous boil offtreatment of the woven greige cloth.

In order to produce cellulose organic acid ester crepe yarn with thedesired creping ability and strength characteristics I have found itnecessary to twist the yarn in the water or other aqueous creping bathat the particular temperature and'under a minimum tension as indicatedabove. For the twisting operation, a down draft twister may be mostconveniently used, hence a trough containing the creping bath may beconveniently mounted below the lower feed roll of such a device. Thefeed roll may be partly immersed in the liquid and the yarn may bepassed completely under the feed roll and out of the trough to theguide, or if the feed roll rotation be reversed, the yarn may comedirectly from the point of contact of the feed roll and its idler roll.In the latter case, the wetting of the yarn is accomplished by contactwith the rolls, whose surfaces are wet as a result of the lower onebeing in contact with the water or aqueous solution. However, up drafttwisters may be employed if provision is made for having the yarn wetduring the act of twisting.

A convenient apparatus of the type first-mentioned is illustrated in theaccompanying drawing in which, i

The application Fig. 1 is a diagrammatic elevation of one form of such adevice and,

Fig. 2 is also a diagrammatic elevational view in partial section of thedeviceof Fig. 1, illustrating the manner in which the yarn is submergedin the creping'bath.

Referring specifically to the drawing, the letters A and B representcellulose acetate yarns of, for example, denier or other desired sizewhich is supplied from a suitable source (not shown). The numeral Idesignates an assembly of rolls by means of which the yarn is caused tobe submerged in the creping bath. Rolls 2 and 3 are idler rolls overwhich the yarn passes to the applicator roll 4 which is positioned withrespect to the trough 5, in such manner that the roll carries the yarnbeneath the surface of the creping liquid 6 contained in trough 5.

Trough 5 is conveniently heated by an electrical resistance unit 1 orother appropriate heating means positioned in chamber 8 forming a partof the trough 5.

Numeral 9 designates a circular yarn guide which is connected to tensionindicator l 0 mounted in convenient proximity to trough 5.- The yarnpassing from the guide 9 passesthrough a guide H adjustably positionedas shown over the center of spindle l2 of the ring spinner l3. Thespindle I2 is driven by means of pulley l4, operated by a source ofpower (not shown). Numeral l5 designates a conventional type of ringprovided with a traveler (not shown).

In Fig. 1 I have shown two ring spinning devices of identicalconstruction which may be operated in such manner that one gives theyarn the so-called Z-twist while the other gives, the yarn the S-twist.The type of twist, as is wellknown, depends merely upon the direction inwhich the spindles are rotated.

The operation of the twisting device is well known in the art and willbe readily apparent from the drawing. Yarn passes around idle rolls 2and 3 as shown, and finally around applicator roll 4, whereby it issubmerged in the creping bath 6, Yarn then is passed to guides 9 and Hto the spool l6, which is driven at a high speed by means of pulley H toinsert a high twist in the yarn. As the yarn passes to the spool, it isballooned out in the manner indicated and twisted to the desired degree.The tension on the yarn is dependent not only upon the speed at whichthe spindle is operated, but also upon the drag produced by thetraveler, and other factors, this tension being measured by means of thetension indicator ll, of a conventional type. Although the temperaturemay be varied widely, depending upon the typeof product being producedand the creping properties desired, I have found that a creping bathtemperature of about 60-65 C. gives highly satisfactory results withyarns of about denier using a twist of 50 turns per inch and a tensionof 10 grams. As indicated, the composition of the aqueous creping bathmay vary rather widely, but I have found that especially good resultsmay be obtained by employing an aqueous dispersion of certain oils suchas olive oil, sulfonated oil, mineral oil and mixtures thereof. Theamount of oil may conveniently be 5-20% of the weight of the water. Whenusing temperatures in excess of 30 C. emulsions are not stable over longperiods of time and hence, I prefer to use water to which a small amountof soap or other wetting agent has been added. Excellent results areobtained by treating the yarn with 140% of the above-mentioned oils andtwisting with water.

As previously stated, it is necessary to assign much more definitelimits to the amount of tension employed than is the case in theordinary crepe twisting of silk and rayon. I have found that the controlof tension is very necessary if the finished yarn is to have thestrength and extensibility necessary to produce a finished commerciallyuseful fabric. Broadly speaking, I find that the best crepe yarn isprepared under conditions of minimum tension during twisting. The lineof demarkation between good and poor crepe yarn is by its very naturesomewhat vague, but, in general, it may be said that it is necessary tomaintain the tension below the point where a given yarn shows apermanent stretch of more than 5% of its original length. I have foundthat especially good results are obtained by ad- Justing the tension sothat the stretch induced in the yarn is from 14%. V

The induced percent stretch may be computed as follows: for example,inches of crepe yarn previously twisted at a tension of 0.1 gram perdenier may serve asa basis of illustration. The take-up of this yarn,that is, the difference between the length of the twisted crepe yarn andthe length of the crepe yarn after untwisting may be represented by thesymbol 6. The final denier of the crepe yarn may be represented by thesymbol Dr and the initial denier by the symbol D.

The denier which the crepe yarn. has after being untwisted is where Dusymbolizes the denier of the untwisted crepe yarn. The per cent stretchgiven the original yarn by the process of crepe twisting is then givenby:

= stretch 'ommended in the prior art wherein it is proposed tostretchthe yarn as much as possible, that is, to employ high tensions intwisting in order to provide for the necessary crepe shrinkage. As-

previously indicated, however, such practices of the prior art areunsatisfactory from the standpoint of producing a satisfactory cre asherein described that I have found it to produce a commerciallysatisfactory crepe.

In the following examples and description I have set forth several ofthe preferred embodiments of my invention but they are included merelyas an illustration and not as a limitation thereof.

Example I. -The twisting bath is made up of distilled water and ofoleate soap, and is maintained at 10 C. by a cooling coil. 150 deniercellulose actate yarn is twisted in one operation to 65 turns per inch,at a spindle speed of 7000 R. P. M., under a tension so adjusted thatthe take-up of a 10-inch sample of the twisted yarn is 2.7 inches. Toattain this tension-about- 12 gm.a No. 26 traveler on a 3-inch ring,with a balloon height of 16 cm. is suitable. However,

' it has been observed that the actual tensions attained with differenttravellers of; the same number are somewhat different, for although thetravelers are identical in weight, there are small differences in shapeand smoothness which result in different tensions. Therefore, thetraveler size and balloon height should be changed until the yarn showsthe desired physical properties. The final denier of the yarn twistedaccording to the above directions willbe about 185-190 and the stretchof the original yarn, were it untwisted, is about 3%. The yarn had abreaking load of 0.80 gram per denier and stretch at break of 20%. Thisyarn is woven in a matelass construction and the fabric is boiled off inwater at 95 C; The resulting product is a true crepe fabric of excellentquality.

Example II.--The twisting bath is made up of water, of oleate soap, andan appropriate fugitive tint to distinguish 8 and Z twists, thetemperature being allowed to assume room temperature. 100 deniercellulose acetate yarn, initially half turn, is twisted in one operationto 83 turns per inch under tension resulting in a takeup of 1.8 inchesin 10 inches of the twisted yarn, a final denier of about 117, and astretch of 1% based on the original yarn. To attain this tension6 to 8gm.a No. traveler is used, with a balloon height of 15 cm. The breakingload of this yarn was 0.83 gram per denier and the stretch at break 25%.The yarn is woven as filling in a 4 x 4 construction, to form a Cantoncrepe upon boiling off.

Example IIL-A twisting bath is prepared of a 10% emulsion of olive oilprepared with triethanolamine and oleic acid and maintained at atemperature of 25 C. 200 denier half-tum cellulose acetate yarn istwisted-in one operation to turns per inch under a tension whichproduces a takeup of 1.9 inches, a final denier around 230, and astretch based on the original yarn of 3.6%. To obtain this tension,around 12 gm. a No. 26 traveler and 15 cm. balloon height are suitable.The breaking load was 0.90 gram per denier and the stretch at break 18%.The yarn is incorporated in a matelass fabric and boiled of! in water at98 C. As in the previous examples, a commercially satisfactory crepefabric results.

Example IV.-A twisting bath is'prepared of water, of potassiumoleatesoap, and appropriate fugitive tint. The bath is maintained at atemperature of 'C. with a tolerance of five degreeseither way. denierhalf-tum cellulose acetate -yarn is twisted in one operation to 68 turnsper inch under a tension resulting in a takeup of 2.85 inches, a finaldenier of 200, and a stretch based on the original yarn of 2.9%. Toobtain this tension-8 gm.a No. 30 traveler and 16 cm. balloon height aresuitable. The breaking load of the yarn was 0.92 gram per denier and theextension at break 20%. This,yarn is woven into a 4 x 4 Canton crepe, 52picks per inch, and

' the fabric is boiled off to give a good crepe appearance.

Example V.-A twisting bath is prepared of water to which is added 0.2%of sulfonated olive oil together with an appropriate fugitive tint. Thebath is maintained at a temperature of 70 C. 158 denier half-turncellulose acetate yarn is twisted to 62 turns-per inch, a final denierof. 182, a stretch of 5.5% being induced. The strength ,nf the crepeyarn is .89 gm. per denier antithe extension at'break is 16%%. To obtainthis tension-8 gm.--a No. 30 traveler is used with balloon height of 16cm. The yarn is woven into a fabric and boiled off in soapy water at90-100 C.

Example VI.-A twisting bath is prepared of water, 0.1% soap, and a tint,the bath being maintained at a temperature of C. 150 denier celluloseacetate yarn is twisted to about 50 turns per inch, the traveler andballoon height being the same as in Example V. The final denier is 165,the induced stretch about 2%. The crepe yarn is then rewound to anotherpackage, in the course of rewinding being sized with a 2.5% solution ofgelatin. The yarn had a breaking load of 0.83 gram per denier andstretch of 24%. This sized yarn is then woven into a fabric which isboiled off in the usual way and is then rinsed,,dyed, tentered and driedin the usual way.

Example VII.A twisting bath is prepared of water to which 0.1% of soapis added together with an appropriate fugitive tint. The bath ismaintained at a temperature of 60 C. with a tolerance of five degrees ineither direction. 150 denier cellulose acetate yarn which has had 10turns per inch inserted during some previous process-for example,spinning or oiling with the oils which have been previously mentioned asbeing beneficial-is twisted to a total of 60 turns per inch under atension which results in a takeup of 2.4 inches, a final denier of 180,and a stretch of the original yarn of 3.3%. To obtain this tension'about8 gm.a traveler size No. 30:.

and balloon height of 16 cm. are suitable. The breaking load of thecrepe yarn was 0.85 gram per denier and it had an extensibility of 21%.This yarn is then woven into a suitable fabric and finished by a hotaqueous treatment.

Although in the above examples I have found it convenient to illustratemy invention by reference to yarns composed of cellulose acetate, thebroad scope of my invention includes the manufacture of crepe yarns inaccordance with the process herein described from yarns composed of orcontaining other cellulose organic acid esters such ascellulosepropionate, cellulose butyrate, cellulose acetate propionate,cellulose acetate butyrate and the like. Likewise, although I have foundit convenient to refer to certain specific deniers, temperatures,tensions, percent stretch and other factors, it will, of course, beunderstood that these are merely illustrative and that my invention isbroadly applicable to the production of crepe-twisted yarns and fabricsproduced therefrom, regardless of the composition and denier of the'yarn, when producedas herein described. The crepe yarns produced asindicated in=the foregoing examples are particularly characterized bythe fact that the filaments comprising the yarn strands receivepractically no longitudinal extension either during the. twisting or inany subsequent operation. This is in direct contradistinction to knownpractice and apparently accounts for the remarkable creping power of mynew type of crepe yarn in comparison with the poor results heretoforeobtained by the practice of the prior art.

Without limiting myself by any particular explanation of the resultsobtained by the prac tice of my invention as herein described, I haveworked out a theory which appears to explain the above-stated facts andthis theory is given for the purpose of providing a more completeunderstanding of my invention. Probably the chief reason why theprevious workers in this field have failed to achieve success istheopinion consistently maintained that the creping. action of a crepe yarnis associated with the ability of the yarn to contract lengthwise whenthe fabric is subjected to whatever influence is used to produce thedesired crepe effect. I have car.- ried out an extensive program ofresearch on the fundamental phenomena of producing this crepe effect andas a result of these studies I have reached the conclusion that the!above premise is false and misleading and that the principal requisiteof a successful crepe yarn is the fact that there has been storedtherein a suitable amount of energy which is released as a torsionalforce during the manufacturing operation wherein the creping power ofthe yarn asserts itself and the crepe pebble appearance appears.Commonly, this is the boiloif operation. Upon the release of thistorsional force, in the yarn by the boil off, the stable configurationof the crepe 'yarn changes from a straight line to a helical spiral andit is the formation of these spirals and not the longitudinalcontraction of the yarn which is chiefly responsible for a genuine crepeeffect.

Further information concerning the potential torque in yarns as well asprocess and apparatus for determining such torque and other relateddetails are set forth in my copending application Serial No. 121,556entitled Manufacture of crepe fabrics. The potential torque in my novelyarns provides another and additional feature. upon which the yarns ofthis invention may be.

further distinguished as will be set forth in more detail hereinafter.The values set forth herein have been arrived at in accordance withprocedure described in my copending application, aforementioned.Briefly, this procedure includes measuring the torque exhibited by yarn-(four strands) after five minutes in Water at a predeterminedtemperature.

I am further of the opinion as a, result of my work on crepe yarns andfabrics that the molecular structure of cellulose acetate and othercellulose organic acid ester filaments is capable of supporting only alimited total internal strain. Whatever part of this availableenergy-absorbing or storing-capacity is taken up by a longitudinalstrain, which upon release causes the filament to contract lengthwise,is deducted from the total amount available for the storing of energyconvertible into torsional forces which distort the crepe yarn into aspiral form and give rise to a crepe effect. It is herein that myprocess of producing cellulose acetate crepe yarns differs from theprevious unsuccessful attempts to cause highly twisted cellulose acetateyarns to crepe. The essential feature of my process is that under mypreferred twisting conditions asmuch as possible of the energystoringcapacity of the yarn is utilized for the storing of torsional forces andas little as possible for longitudinal forces.

The cellulose acetate crepe yarns made by my process are subjectedpreferably to degrees of twist approximately equal to the twists nowcustomarily inserted in regenerated cellulose crepe yarns. The degree oftwist used depends upon the denier and the type of effect it is desiredto produce, but in general it is sufiicient to duplicate many knowncrepe cloths now constructed with the use of regenerated cellulose crepeyarns by substituting therefor cellulose acetate crepe yarns of the samedenier and Thus, for most purturns per inch, 150 denier yarn turns perinch, and 200 denier yarns 50 turns per inch, the denier numbersreferring to the untwisted yarn.

. This feature of my invention iurther serves to diiferentiate it fromsuch processes as have hitherto been described which have as their ob-Ject softening or otherwise conditioning the yarn to enable it toaccommodate extremely high degrees of twist Cellulose acetate crepeyarns produced in accordance with the process herein described arerather sharply distinguished from the so-called crepe yarns of the priorart.

They are particularly distinguished by the following features: I l

denier. O (1) Extension at break.-High-of the order of (a) Physicalappearance-Crepe yarn is rough and has some rough feel as ischaracteristic of rayon crepe yarns.

(h) Crepina power.-High-comparable with similar rayon crepe yarns.

(0 Potential torque-Varies, depending on denier-in the order 0! at least500 dyne centimeters for 100 denier yarn (about 700 preferred), 1300dyne centimeter for a150-denier yarn (1400 preferred) and.

1600 dyne centimeters for 200 denier yarn (about 1900 preferable).Values for intermediate and other denier, oi' an order proportional tothose stated.

0! above en urnerated properties and characteristics, that set forthrelative to twists of about 50-85 turns per inch (depending on denier),

and under headings (b), (c), (I) are believed to be the mostsignificant.

What I claim and desire to secure by Letters Patent of the United Statesis:

1. A cellulose organic acid ester crepe twisted yarn having a twistinthe order of from turns per inch for denier to 50 turns for 200denier, said yarn after twisting having a final denier approximately-125% of its original denier, a twist takeup of approximately l5-25%, anextension of not over about 5% and a breaking load of the order of0.8-0.9 gram per denier and an extension at break of the order of 15-25%of its length, and having the ability, when woven into an appropriateconstruction, of producing a true crepe fabric when the twist isreleased.

2. A cellulose organic acid ester crepe twisted yarn having a twist inthe order of from 65 turns per inch for 100 denier to 50 turns for 200denier, said yarn after twisting having a final denier approximately110-125% of its original denier. a twist takeup of approximately l5-25%,an extension at break of the order of 15-25% of its length, and havingthe ability, when woven into an appropriate construction, of producing atrue crepe fabric when the twist is released.

3. A cellulose organic acid ester crepe twisted yarn having a twist inthe order of from 65 turns per inch for 100 denier to 50 turns for 200denier, said yarn after twisting having a final denier approximately110-125% of its original denier, a twist takeup of approximately 15-25%,a breaking load of the order of 0.8-0.9 gram per denier, an extension atbreak of the order of 15-25% of its length, and having the ability, whenwoven into an appropriate construction, of producing a true crepe fabricwhen the twist is released.

4. A cellulose organic acid ester crepe twisted yarn having a twist inthe order of from 65 turns per inch for 100 denier to 50 turns for 200denier, said yarn after twisting having a final denier approximately110-125% of its original denier, a twist takeup of approximately 15-25%,an extension of not over about 5%, an extension at break of the order of15-25% of its length, and having the ability, when woven into anappropriate construction, of producing a true crepe fabric when thetwist is released.

. 5. A cellulose organic acid ester crepe twisted yarn having a twist inthe order of from 65 turns per inch for 100 denier to 50 turns for 200denier, said yarn after twisting having a final denier approximately110-125% of its original denier, a twist takeup of approximately 15-25%and having the ability, when woven into an appropriate construction, ofproducing a true crepe fabric when the twist is released.

6. The product of claim 2 in which the crepe twisted yarn is composed ofcellulose acetate.

7. A crepe fabric containing crepe yarns produced in accordance withclaim 2.

8. A cellulose organic acid ester crepe twisted yarn having a twist inthe order of from 65 turns per inch for 100 denier to 50 turns for 200denier, said yarn having a potential torque in the order of at least 500dyne cm. for 100 denier yarn, 1300 dyne cm. for a denier yarn and 1600dyne cm. for 200 denier yarn, and having the ability, when woven into anappropriate construction, of producing a true crepe fabric when thetwist is re-- leased.

JAMES G. MONAILY. 60

